Swage type fastener

ABSTRACT

A fastening system is provided that includes a fastener having a pin member with a lock groove and crest geometry that is optimized to receive swaged material from collars of materials of different strengths for securing workpieces for different load applications. The lock grooves have the longest width required for collars of lower strength for one application or greater strength for a second application and the crests have the longest width required for collars of greater strength for the second application whereby satisfactory clamp and tensile loads and resistance to failure will result when the lock grooves are filled with collar materials of different strengths. The lock groove and crest geometry is of a uniform construction for the plurality of applications with pin members of a common diameter. Certain collars of different materials have similar outside diameters for installation by a tool having a swage anvil with a uniform swage cavity that swages the collars into the lock grooves for securing workpieces in shear, shear/tension, shear composite and shear/tension composite applications. A method of designing a fastener is also provided that has a uniform lock groove and crest geometry for use in the plurality of applications.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. Ser. No.10/186,940, filed Jun. 28, 2002, which is a continuation-in-partapplication of U.S. Ser. No. 10/117,741, filed Apr. 5, 2002, nowabandoned.

FIELD OF THE INVENTION

The present invention relates to a two piece, swage type fastenerincluding a pin and a collar with the collar adapted to be swaged intolock grooves on the pin and more particularly to swage type fastenersthat have an optimized lock groove and crest design for use in aplurality of applications with a plurality of collars of differentmaterials and strength. The optimized lock groove and crest design canbe used in a plurality of applications due to the lock grooves andcrests being able to receive swaged materials from collars made ofdifferent materials and strength during swage. A method of designing afastener is also provided that has a lock groove and crest geometry thatis optimized and is provided as a uniform construction for use in theplurality of applications with collars of different materials andstrength.

BACKGROUND OF THE INVENTION

Swage fasteners can be of a pull type or stump type. A typical swagetype fastener includes a pin and a collar with the pull type fastenerhaving a pin shank having a locking portion with lock grooves and a pullportion with pull grooves. The pull grooves are adapted to be gripped bymatching teeth in chuck jaws of an installation tool having a swageanvil adapted to engage the collar whereby a relative axial force can beapplied between the pin and collar to move the anvil over the collar toswage it into the lock grooves.

With respect to swage fasteners of the pull type, the pull portion isconnected to the lock groove portion via a breakneck groove of reducedstrength which is adapted to fracture at a preselected magnitude ofaxial tensile force greater than required to swage the collar wherebythe pull portion, or pintail, will be severed and removed from the pinshank after completion of swaging. The breakneck groove is of sufficientstrength to withstand the high tensile load for swaging and the pullgrooves must be similarly of sufficient strength to accept the relativeaxial pull load applied by the engaged teeth of chuck jaws of theinstallation tool. This routinely requires that the pull portion be of arelatively large diameter so as to have sufficient material to providethe necessary size and strength for the breakneck groove and also toinhibit fracturing of the pull grooves instead of the breakneck groove.

A typical stump type fastener includes a pin and a collar that has a pinshank having a locking portion with lock grooves. The difference betweena swage fastener of the pull type and the stump type is that the stumptype does not have a pull portion with pull grooves. Also, in the stumptype fastener system, an installation tool is used that has a swageanvil adapted to engage the collar to apply a relative axial forcebetween the pin and collar to move the anvil over the collar to swage itinto the lock grooves and a bucking member that is used to engage thepin head.

U.S. Pat. Nos. 6,325,582, 6,233,802, 5,125,778, 5,090,852, 5,049,016,4,867,625, 4,813,834, 4,472,096, 4,221,152 and 4,208,943 were issued tothe assignee of the present invention or a predecessor in interest.These patents all relate to various swage fastener designs and arerepresentative of the art. In the prior art, a fastener was typicallyoptimized for a particular collar for a particular application. Also, inthe prior art, fasteners typically had a single grip range. A singlegrip range means that a fastener could fasten workpieces that havevariations in thickness of {fraction (1/16)} of an inch.

The optimization technique employed by the present invention departsfrom the prior art practice of optimizing a fastener for a particularcollar for a particular application. In the present invention, the lockgroove and crest geometry is optimized for use in a plurality ofapplications wherein the lock grooves and crests are each provided withthe longest width required for a specific application to provide thefastening system with satisfactory clamp and tensile loads andresistance to failure in the plurality of applications when the lockgrooves are filled with various materials from different collars ofvarious strengths. Also, the lock groove and crest geometry is of auniform construction that is used in the plurality of applications thatenables the lock grooves and crests for each pin diameter to bemanufactured with tooling that uses a common lock groove and crestgeometry. Such an approach reduces costs associated with the tooling.

Additionally, for each pin size, certain collars of different materialshave about the same outside diameter so an installation tool with auniform swage anvil geometry can be used to swage those collars ofdifferent materials into the lock grooves to install the swage typefastener in workpieces for shear, shear/tension, shear composite andshear/tension composite application. Such an approach reduces the costsassociated with labor in exchanging a swage anvil in the tool that isused in such applications.

Furthermore, the fastener of the present invention has a double griprange. Double grip means that a fastener can fasten workpieces that varyin thickness up to ⅛ of an inch. Such an approach increases theversatility of the fastener.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a swage typefastener having a pin member with a lock groove and crest geometry thatis optimized that is capable of having collars of various materials andstrength swaged into the lock grooves with the lock grooves and crestsbeing of a uniform construction for each pin diameter for use inconnection with collars of different materials and strength.

It is another object of the invention to provide a swage type fastenerhaving a pin member with a lock groove and crest geometry that isoptimized that is capable of having collars of various materials andstrength swaged into the lock grooves wherein the various materialsprovide the fastener with different clamp and tensile loads for use in aplurality of applications.

It is yet another object of the invention to provide a swage typefastener having a pin member with a lock groove and crest geometry thatis optimized that is capable of having collars of various materials andstrength swaged into the lock grooves wherein certain collars have aboutthe same outside diameter that enables a common installation tool havinga swage anvil with a uniform swage cavity to be used to swage thesecollars of different materials into the lock grooves to install theswage type fastener in workpieces for shear, shear/tension, shearcomposite and shear/tension composite applications.

It is yet another object of the present invention to provide a swagetype fastener that has a double grip range.

It is yet another object of the invention to provide a method ofdesigning a swage type fastener with a lock groove and crest geometrythat is optimized that is capable of having collars of various materialsand strength swaged into the lock grooves wherein the various materialsprovide the fastener with different clamp and tensile loads for use in aplurality of applications.

Certain objects of the invention are achieved by a fastening system thatincludes a fastener, for securing a plurality of workpieces together,the fastening system having a pin member having a lock groove and crestgeometry that is optimized. The optimized lock groove and crest geometryis adapted to receive swaged material from a plurality of collars ofdifferent materials and strengths for securing workpieces in differentapplications having different load requirements, wherein the lockgrooves are provided with the longest width required for collars oflower strength for one application or greater strength for a secondapplication and the crests are provided with the longest width requiredfor collars of greater strength for the second application whereby thefastening system will provide satisfactory clamp and tensile loads andresistance to failure in the plurality of applications when the lockgrooves are filled with collar materials of different strengths. Such anoptimization results in an overall minimization of size and weight ofthe fasteners with lock grooves and crests of a uniform construction foruse with collars of different materials and strength. The lock grooveand crest geometry for the pin member is of a uniform construction thatis used in the plurality of applications with one or more pin members ofa common diameter. Certain collars of different strengths are providedwith about the same outside diameter. Such a construction permits use ofa common installation tool having a swage anvil with a uniform swagecavity that swages such collars of different strengths into the lockgrooves of the pin member for installing the swage type fastener inworkpieces for shear, shear/tension, shear composite and shear/tensioncomposite applications.

Other objects of the invention are achieved by a method of designing afastener to be used in a fastening system. The method includes obtainingthe clamp and tensile load requirements for a plurality of applications,optimizing the lock groove geometry by providing the lock grooves withthe longest width required for collars of lower strength for oneapplication or greater strength for a second application and optimizingthe crest geometry by providing the crests with the longest widthrequired for collars of greater strength for the second application.This method permits standardizing the optimized lock groove and crestgeometry for the pin member for use of the swage type fastener in aplurality of applications with one or more pin members of a commondiameter. Also, certain collars of different strength materials areprovided with about the same outside diameter that are adapted to beswaged into the lock grooves to provide the fastening system withsatisfactory clamp and tensile loads and resistance to failure in shear,shear/tension, shear composite and shear/tension composite applications.

Swage type fasteners are used for a variety of different applicationsincluding the joining of workpieces of various types of materials with apredetermined clamp and tensile load. For example, in aircraftapplications, the workpieces can be of a lightweight metal such asaluminum or can be made of composite materials. The swage type fastenerof the present invention is particularly useful because it may be usedin connection with fastening metallic workpieces, composite workpiecesor combinations thereof. As such, the swage type fastener of thisinvention is particularly advantageous in that it can be used in avariety of applications due to the ability of the optimized lock groovesof the pin member to be filled with various materials of differentcollars.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal view with some portions shown in section andothers shown broken away of a fastener of the present invention inassembly relationship with a portion of a tool shown as applied to thefastener prior to installation and for securing workpieces;

FIG. 2 is a view similar to that of FIG. 1 showing the fastener securingworkpieces at a minimum grip of the tool and with the swage anvil of thetool shown in the engaged, installed condition;

FIG. 3 is a view similar to that of FIG. 2 showing the fastener securingworkpieces at a maximum grip of the tool and with the swage anvil of thetool shown in the engaged, installed condition;

FIG. 4 is an enlarged fragmentary view taken in the circled area 4 inFIG. 3 of the lock grooves of the pin;

FIG. 5 is a fragmentary enlarged view of one of the lock grooves of FIG.4; and

FIG. 6 is a sectional view of a fastener similar to that of FIGS. 1-3and with the fastener being of a stump type instead of a pull type andfor securing workpieces of a maximum thickness for the fastener.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Looking now to FIGS. 1 and 2, a fastener 10 is shown to include a pinmember 12 and tubular collar 14. Pin member 12 has an elongated shank 15which extends through aligned openings 16 and 17 in a pair of workpieces18 and 20, respectively, to be secured together. An enlarged protrudinghead 22 at one end of shank 15 engages one side of workpiece 18.Adjacent the head 22, the shank 15 has a straight portion 24 which isadapted to be received within aligned bores 16 and 17 with a slightclearance fit or interference fit. Following the straight portion 24 isa plurality of circumferentially extending, annular lock grooves 26. Atransition portion 28 smoothly connects the lock grooves 26 withstraight shank portion 24.

A breakneck groove 40 is located adjacent the lock grooves 26 anddefines the weakest portion on the shank 15. A straight land 42 islocated between the breakneck groove 40 and a plurality of pull grooves44. The land 42 is of a reduced diameter relative to the shank portion24, the lock grooves 26 and the pull grooves 44. The pull grooves 44 areadapted to be gripped by a tool 48 which is actuable to set the fastener10. The tool 48 can be generally constructed in a manner known to thoseskilled in the art and therefore is only partially shown for purposes ofsimplicity. Briefly, the tool 48 has a plurality of jaws 50 adapted togrip the pin 12 at pull grooves 44. Jaws 50 are located in a tubularcollet assembly 52 which is slidably supported in an anvil housing 54which terminates at one end in a swage anvil portion 56.

The symmetrically shaped, tubular collar 14 is adapted to be locatedover the pin shank 15 and, with the workpieces 18, 20 pulled together,will be in radial alignment with some of the lock grooves 26. Withactuation of the tool 48, a relative axial force is exerted between thepin 12 and collar 14 resulting in swage anvil portion 56 swaging thecollar 14 into the lock grooves 26 of pin 12. Upon completion of theswaging, the shank 15 will be severed at the breakneck groove 40, asshown in FIG. 2. Subsequently, upon further actuation of the tool 48, acollar ejector member 58 will be urged forwardly to eject the swagedcollar 14 from the anvil portion 56 thus completing the installation.FIG. 3 depicts the fastener 10 in an engaged, installed position withworkpieces 18 and 20 of a maximum grip with workpieces 18 and 20 beingof a maximum total thickness of the fastener 10. The workpieces 18 and20 can vary in thickness by {fraction (1/8)} inch and can still befastened together with the fastener 10 of the present invention becausethe fastener 10 has a double grip range. Such an approach increases theversatility of the fastener 10 in securing workpieces 18 and 20 ofvarying thickness.

As can best be seen in FIGS. 4 and 5, the lock grooves 26 and annularcrests 60 are of a unique design that are optimized for a pin member ofa preselected diameter for use in a plurality of applications withcollars 14 of different materials and strength. The optimizationtechnique employed by the present invention departs from the prior artpractice of optimizing a fastener for a particular collar for aparticular application. In the present invention, the lock groove 26 andcrest 60 geometry is optimized for use in a plurality of applicationswherein the lock grooves and crests are each provided with the longestwidth required for a specific application to provide the fasteningsystem with satisfactory clamp and tensile loads and resistance tofailure in the plurality of applications when the lock grooves arefilled with various materials from different collars of variousstrengths. The optimized design can be used for all applications thatinvolve the use of that pin diameter and enables the lock grooves 26 andcrests 60 for that pin diameter to be manufactured with tooling thatuses a common lock groove and crest geometry. Such an approach reducesthe costs associated with the tooling.

The lock grooves 26 are capable of receiving materials of differentstrength from collars 14 during swage. The lock grooves 26, which areseparated by crests 60 can be considered to be defined by a root portion62, which is connected at one end to a leading transition portion 64 andat the opposite end to a trailing transition portion 66. In order todesign a swage type fastener with lock grooves 26 and crests 60 of auniform construction for use in a plurality of applications, the lengthof the lock grooves 26 and the length of the crests 60 are eachoptimized with reference to the clamp and load requirements forapplications for each pin diameter for collars 14 of differentmaterials. For example, Table 1 was used to optimize the length of thelock grooves 26 and crests 60 for each of a plurality of different pindiameters for use with collars of different materials for a plurality ofapplications. TABLE 1 Minimum Mechanical Performance of Pin Member ofVarious Diameters in Relation to Various Collars for DifferentApplications Mechanical Performances (lbs.) Type of application: ShearShear/Tension Tension Material to join: Metal Metal Metal Lock Grooves:5 5 6 Titanium 3-2.5 Pin Titanium 3-2.5 Stainless Diameter CollarMaterial Aluminum Stainless 303 303 {fraction (5/32)}″ Tensile 1,4001,700 2,300 Clamp 700 850 1,150 {fraction (3/16)}″ Tensile 1,600 2,4002,750 Clamp 800 1,200 1,375 {fraction (7/32)}″ Tensile 2,250 3,450 3,880Clamp 1,125 1,725 1,940 ¼″ Tensile 3,000 4,500 5,000 Clamp 1,500 2,2502,500 {fraction (5/16)}″ Tensile 5,000 6,850 8,300 Clamp 2,500 3,4254,150 ⅜″ Tensile 7,000 10,200 12,700 Clamp 3,500 5,100 6,350 {fraction(7/16)}″ Tensile 9,500 13,100 19,000 Clamp 4,750 6,550 9,500 ½″ Tensile12,500 18,000 25,500 Clamp 6,250 9,000 12,750

With reference to the specific clamp and tensile loads required by Table1 for particular applications, the lock grooves 26 were optimized for aspecific application for each pin diameter as follows.

Equation 1 defines the available shear area for the lock grooves 26:ΠD _(MAJOR) N G _(W) =Shear Area  (Equ. 1)wherein:

-   -   D_(MAJOR) is the major diameter of the crests 60;    -   N is the minimum number of lock grooves 26 on the pin member 12        engaged by the swaged material of the collar 14 over the grip        range of the fastener 10; and    -   G_(W) is the groove width of the lock grooves 26.

Equation 2 defines the amount of tensile load that the lock grooves 26would be able to control:T×Shear Area=Tensile Load  (Equ. 2)wherein:

-   -   T is the shear strength of the collar 14 material; and    -   Shear Area is the value from Equation 1.

In the case of the present invention, the G_(W) of the lock grooves 26is optimized to provide the longest groove width for a specificapplication that can be used in all applications for the loadrequirements of a specific pin diameter. The longest groove widthrequired for a specific application for a specific pin diameter is thenused as the standard groove width for that specific pin diameter. Incertain embodiments, the G_(W) of the lock grooves 26 is optimized foraluminum 2024T4 alloy in shear applications. In alternate embodiments,the G_(W) of the lock grooves 26 is optimized for titanium 3A1-2.5Valloy in tension applications. Generally, aluminum 2024T4 alloy is oflesser strength than stainless 303 SE alloy steel and titanium 3A1-2.5 Valloy and stainless 303 SE alloy is considered to be about equal instrength to titanium 3A1-2.5 V alloy. See Table 2 set forth herein for acomparison of material properties. Typically, the G_(W) of the lockgrooves 26 of the present invention are optimized to provide thefastening system with a strength equal to or greater than one hundredten percent (110%) of a customer's tensile load requirements for aparticular application.

After standardizing the groove width for a specific application for aspecific pin diameter, the crests 60 were optimized for each pindiameter as follows.

Equation 3 defines the available shear area for the crests 60:ΠC _(D)N C′_(W) =Shear Area  (Equ. 3)wherein:

-   -   C_(D) is the effective crest diameter of the crests 60 wherein        C_(D) is equal to about D_(MAJOR)−C_(h);    -   N is the minimum number of lock grooves 26 on the pin member 12        engaged by the swaged material of the collar 14 over the grip        range of the fastener 10; and    -   C′_(W) is the effective crest width at about half the height of        C_(h).

Equation 4 defines the amount of tensile load that the crests 60 wouldbe able to control:T×Shear Area=Tensile Load  (Equ. 4)wherein:

-   -   T is the shear strength of the pin member 12; and    -   Shear Area is the value from equation 3.

The C′_(W) of the crests 60 are optimized for each pin diameter to beable to resist failure when the lock grooves 26 are filled with a collar14 of a relatively higher strength material such as titanium 3A1-2.5Valloy in tension applications. Typically, for the majority of thevarious pin diameters of the pin member 12, the G_(W) of the lockgrooves 26 is optimized for aluminum 2024 alloy in shear applicationsand the C′_(W) of the crests 60 is optimized for titanium 3A1-2.5V alloyin tension applications. While it could be stated that such an approachonly partially optimizes the lock groove 26 and crest 60 design of thefastener 10 because the lock grooves 26 and crests 60 are optimized fordifferent applications, the lock grooves 26 and crests 60 arenonetheless optimized for use across a plurality of applications becausethe fastener 10 provides satisfactory clamp and tensile loads andresistance to failure in the plurality of applications when the lockgrooves 26 are filled with different collar 14 materials. In othercases, where the G_(W) of the lock grooves 26 and the C′_(W) of thecrests 60 are both optimized for titanium 3A1-2.5V alloy in tensionapplications, the G_(W) of the lock grooves 26 is not greater than tenpercent (10%) of the width of the lock grooves 26 if the lock grooves 26had been optimized for aluminum 2024T4 alloy. While it could be statedthat such an approach fully optimizes the lock groove 26 and crest 60design of the fastener 10 for the tension application because the lockgrooves 26 and crests 60 are both optimized for the same application,the lock grooves 26 and crests 60 are nonetheless optimized for useacross a plurality of applications because the fastener 10 providessatisfactory clamp and tensile loads and resistance to failure in theplurality of applications when the lock grooves 26 are filled withdifferent collar 14 materials.

Typically, the C′_(W) of the crests 60 of the present invention areoptimized to provide the fastening system with a strength equal to orgreater than one hundred twenty percent (120%) of a customer's tensileload requirements for a particular application for a particular pindiameter. In the preferred embodiment of the invention, the pin member12 is manufactured from titanium 6A1-4V alloy, the G_(W) of the lockgrooves 26 has the longest groove width that is required for a specificapplication to provide satisfactory clamp and tensile loads in allapplications for a specific pin diameter, the C′_(W) of the crests 60 isoptimized to avoid failure when the lock grooves 26 are filled withtitanium 3A1-2.5V alloy and the pin diameter falls within the range offrom around {fraction (5/32)} inch to around {fraction (1/2)} inch.

After the lock grooves 26 and crests 60 are each optimized for aspecific application in each of the plurality of different pindiameters, an appropriate collar 14 of a preselected material and acalculated outside diameter is selected for swaging into the lockgrooves 26 to provide the fastening system with satisfactory clamp andtensile loads for a selected application. Typically, a collar 14 made ofaluminum 2024 alloy would be used in shear applications and a collar 14made of stainless 303SE alloy steel or titanium 3A1-2.5V alloy would beused in shear/tension or tension applications. To obtain the desiredclamp and tensile load for each of the applications, the calculatedoutside diameter of the collar 14 is modified through experimentationwhile keeping the lock groove 26 and crest 60 geometry and the diameterof the throat (Da of FIG. 1) of the swage anvil 56 portion constant.Through experimentation, the outside diameter of the modified collars 14of different materials only have slight variations in the outsidediameter that enables the modified collar 14 to be swaged into the lockgrooves 26 with a swage anvil 56 that has a uniform swage anvil cavityfor shear, shear/tension, shear composite and shear/tension compositeapplications. It has been found that a collar 14 of about the sameoutside diameter does not work well in tension and tension compositeapplications. Therefore, a collar 14 of greater outside diameter and adifferent swage anvil 56 is used for tension and tension compositeapplications.

Such a uniform swage anvil portion 56 provides the customer with theadditional benefit of being able to install collars 14 with a commoninstallation tool 48 for many applications for a specific pin diameter.This feature provides the customer of the fastener 10 with the benefitof only needing to keep an inventory of a single tool with a uniformswage anvil portion 56 for a specific pin diameter for use in shear,shear/tension, shear composite and shear/tension composite applications.Such an approach would minimize the time required for an operator toexchange swage anvils in tools for use in other applications for aspecific pin diameter. As can be appreciated, the savings on labor to anend user due to such an approach would be substantial.

The load requirements provided in Table 1 to design the fastening systemof the present invention would also be useful across the board for therange of load requirements for shear, shear/tension and tensionapplications for use in the field of commercial and military aircraftbecause both types of aircraft have a similar range of load requirementsfor shear, shear/tension and tension applications. Therefore, thefastening system of the present invention would additionally be valuablefor use in commercial and military aircraft applications.

As can readily be seen from Table 1, different collar materials may beutilized with the optimized lock groove 26 and crest 60 design for eachpin diameter in shear, shear/tension or tension applications to obtain avariety of tensile and clamp loads. It should be noted that thedifferent applications may require more or less lock grooves 26 thanother applications. In any regard, for a specific pin diameter, the lockgroove 26 and crest 60 geometry remains constant. Also, for pull typeswage fasteners, different applications would require breakneck grooves40 adapted to fracture at different magnitudes of axial tensile forcebased on the swage load requirements for a particular application.Conversely, stump type fasteners would not have the limitation of thebreakneck groove because such a fastener does not have a breakneckgroove. Also, there may some applications where a removable mandrelcould be utilized in place of a severable pintail or a tool with athreaded external drive and/or threaded mandrel for an internal drivesuch as shown in U.S. Pat. No. 5,604,968. In the preferred embodiment ofthe invention, the optimized lock grooves 26 for each pin diameter isable to receive a collar 14 of various materials such as titanium, steeland aluminum alloys for various applications. As can be appreciated, thecollars 14 of different materials provide a variety of preselected clampand tensile loads for the optimized lock grooves 26 and crests 60 of aspecific pin diameter.

Table 1 relates to fastening workpieces 18 and 20 of metal, i.e. such asaluminum. It should be understood that a similar table of values couldbe provided for applications where the workpieces 18 and 20 would bemade of a composite material. While collar 14 is shown as a tubularcollar 14 in FIGS. 1-3 for securing workpieces 18 and 20 of metal, aflanged type collar would be used to secure workpieces made of compositematerials. Also, while particular attention is given to collars made ofaluminum 2024T4 alloy, titanium 3A1-2.5V alloy and stainless 303 SEalloy steel in Table 1, one of skill in the art would appreciate thatother aluminum alloys, other titanium alloys, other steel alloys orother metallic alloys or materials could be used for the collars 14 witha pin 12 having lock grooves 26 and crests 60 of a uniform geometry andwould provide different tensile and clamp loads for shear,shear/tension, tension or other applications.

The following Examples demonstrate the magnitude of shear and tensilestrengths between shear, shear/tension and tension applications.

EXAMPLE 1 Magnitude of Minimum Shear Strength in ksi and Minimum TensileRequirement in Pounds for {fraction (5/32)} Inch Pin Diameter

Type of Lock Grooves Collar Min. Min. Application Actual Used MaterialShear Tensile Shear 5 5 Aluminum 37 1,400 2024 Shear/Tension 5 5Titanium 58 1,700 3Al-2.5 V Tension 6 6 Titanium 58 2,300 3Al-2.5 V

As can be seen from Example 1, the ratio of shear strengths betweenshear and tension applications is about 64% and the ratio of tensilestrengths between shear and tension applications is about 61%.

EXAMPLE 2 Magnitude of Minimum Shear Strength in ksi and Minimum TensileRequirement in Pounds for {fraction (7/16)} Inch Pin Diameter

Type of Lock Grooves Collar Min. Min. Application Actual Used MaterialShear Tensile Shear 5 5 Aluminum 37  9,500 2024 Shear/Tension 5 5Titanium 58 13,100 3Al-2.5 V Tension 6 6 Titanium 58 19,000 3Al-2.5 V

As can be seen from Example 2, the ratio of shear strengths betweenshear and tension applications is about 64% and the ratio of tensilestrengths between shear and tension applications is about 50%.

Furthermore, as can be seen from FIG. 5, the fastener of the presentinvention is further defined by the following relationships:

-   -   P is equal to G_(W)+C_(W)    -   R_(R) is equal to G_(W)    -   C_(h) is equal to 4I    -   B_(R) is equal to 0.005 inch for pin diameters of {fraction        (5/32)} to ½ inch        The fastener of the present invention is further defined by the        relationships:    -   For pin member diameters of ⅜, {fraction (7/16)}and ½ inch,        C_(h) is equal to D_(S)×0.03125    -   For pin member diameters of {fraction (5/32)}, {fraction        (3/16)}, {fraction (7/32)}, ¼ and {fraction (5/16)} inch, C_(h)        is equal to (D_(S)×0.03125)+0.002        In the above relationships:    -   P=pitch;    -   G_(W)=the lock groove 26 width;    -   C_(W)=the crest 60 width;    -   R_(R)=root radius;    -   C_(h)=the crest 60 height;    -   I=the distance between a horizontal tangent to the root radius        and a horizontal tangent to the intersection of the root portion        62 and the trailing portion 66;    -   D_(S)=the diameter of the straight portion 24; and    -   B_(R)=blend radius.

In one form of the invention, the leading transition portion 64 wasprovided to be at a 40 degree angle with a plane transverse to the axisof pin 12 while the trailing transition portion 66 was provided to be ata steeper angle of 20 degrees. The angle of the leading portion 64facilitates flow of the material of collar 14 in swage while the steeperangled trailing portion 66 provides a buttressing effect to contain theswaged collar material. This buttressing effect facilitates clamping ofthe workpieces 18 and 20 as the collar 14 elongates during swage. Thetransition portions 64 and 66 intersect the roundlike root portion 62whereby a smooth transition is provided.

With this lock groove 26 construction, it is desirable to provide thecollar 14 with a volume such that when swaged into the lock grooves 26it will have an excess volume over that required to fill the lockgrooves 26. In one embodiment, the volume of collar 14 was selected toprovide ‘overpacking’, i.e., a volume of collar 14 to providesubstantially more volume of collar material for filling lock grooves 26than it could normally accept within the swage envelope defined by thethroat 36 of the swage cavity of anvil 56 and the confronting portion ofpin 12 (see FIG. 1). In the present system, it has been found desirableto provide a volume of collar material which has an excess of at leastaround 17% to around 25% for the various collar 14 materials that areused. The percentage ‘overfill’ or ‘overpacking’ noted can be generallydetermined for a finite length of the effective swage portion of throat36 (see FIG. 1) by the relationship:${100x\frac{\left\lbrack {\left( {{Dc}^{2} - {ID}^{2}} \right) - \left( {{Da}^{2} - {Dm}^{2}} \right)} \right\rbrack{dl}}{\left\lbrack {{Da}^{2} - {Dm}^{2}} \right\rbrack{dl}}} = {\%\quad{overfill}}$wherein:

-   -   Da is the diameter of the throat 36 of anvil 56;    -   Dc is the outside diameter of the collar 14 before swage;    -   ID is the inside diameter of the collar 14 before swage;    -   Dm is the mean diameter of the lock grooves 26; and    -   dl is considered to be a finite length within the swage portion        of throat 36.

It is also desirable that the pin member 12 be hard enough relative tothe hardness of the collar 14 to resist crushing or substantial yieldingin tension from the high compressive swage loads of different collarmaterials. In a preferred embodiment, it was found that the followingmaterial properties of the pin member 12 and collars 14 set forth inTable 2 satisfied the requirements of the fastening system of theinvention: TABLE 2 Material Properties for Pin Member and CollarsMinimum Minimum Tensile Shear Young's Strength Strength Modulus DensityMaterial Usage (ksi) (ksi) (msi) (pci) Titanium Pin 165.0 95.0 16.00.160 6Al-4 V alloy Member Titanium Collar 99.0 60.0 15.0 0.162 3Al-2.5V alloy Stainless 303 Collar 89.9 61.6 28.8 0.289 SE alloy AluminumCollar 62.0 37.0 10.5 0.101 2024T4 alloy

Generally, in the present invention, it is desirable to utilize a pinmember 12 and collar 14 to provide a fastening system that has desirableclamp strengths and pin yields to provide the pin member 12 with asufficient hardness to accept both the high tensile preloads desired andthe swage loads on the collar 14 substantially without yielding. Inorder to realize high clamp loads, the collar 14 must have a sufficientwall thickness and, therefore, volume to insure that enough collarmaterial will move axially in elongation. At the same time it isdesirable that the swaged collar have sufficient wall thickness and,therefore, have sufficient strength to resist any significant springback from the lock grooves 26. The collar wall also should havesufficient thickness to resist significant radial expansion undertensile load such that the crests 60 and collar shoulders remain insubstantially full engagement as the design tensile load on the joint isreached. If the wall does not provide sufficient radial stiffness, thecollar 14 could expand radially under tensile load, reducing theeffective shear plane carrying the load. The result could be a prematurefailure in shear at the tips of the crests 60 or collar 14 shoulders. Inthis regard, the required wall thickness of the collar 14 will increaseas a function of its diameter Dc. Thus, the final swaged wall thicknessmust be sufficient to withstand at least the minimum design tensile loadsuch that failure will occur in shear generally across the maximumeffective shear plane of the collar 14. If the collar wall is too thick,it will impede swaging and require excessive installation loads.

Thus, the collar wall thickness is selected to provide the necessarymaterial to promote swaging into the lock grooves 26 and flow inelongation of the pin member 12 to provide the desired clamp load. Atthe same time, the collar wall thickness at final swage is also selectedto provide sufficient, radial stiffness or hoop strength to resistsignificant radial spring back from the lock grooves 26 both duringinitial swage and also under subsequent tensile loading. Also, thevolume of the collar 14 and swage cavity 36 are selected to providemovement of the material of collar 14 into the lock grooves 26 to assurea good fill. In this invention, it was found that between around 17%-25%overfill of the lock grooves 26 provided satisfactory results. In thisregard, an overfill significantly under 17% would not provide thedesired high preloads while an overfill significantly over 25% couldresult in excessive installation loads which could yield the pin member12.

The embodiments of FIGS. 1-3 show pull type fasteners; the features ofthe present invention, however, are also applicable to a stump typefastener as shown in FIG. 6. In the description of the embodiment ofFIG. 6, components similar to like components in the embodiments ofFIGS. 1-3 have been given the same number designation with the additionof the letter subscript “b”. Except for the pull portion of FIGS. 1-3,the other elements of the fastener 10 provided in the embodiment ofFIGS. 1-3 are provided in the embodiment of FIG. 6 and for the sake ofbeing concise, FIG. 6 will only be briefly addressed herein because oneof ordinary skill in the art would understand that fastener 10 b of FIG.6 is similar in design and operation to the fastener 10 of FIGS. 1-3.

Looking now to FIG. 6, a fastener 10 b is shown to include a pin member12 b and tubular collar 14 b. Pin member 12 b has an elongated shank 15b which extends through aligned openings 16 b and 17 b in a pair ofworkpieces 18 b and 20 b, respectively, to be secured together. A head22 b at one end of shank 15 b engages one side of workpiece 18 b.Adjacent the head 22 b, the shank 15 b has a straight portion 24 b whichis adapted to be received within bores 16 b and 17 b with a slightclearance fit or interference fit. Following the straight portion 24 bis a plurality of circumferentially extending, annular lock grooves 26b. A transition portion 28 b smoothly connects the lock grooves 26 bwith straight shank portion 24 b.

The fastener 10 b is adapted to be set by a tool assembly 48 b of asqueeze type which can generally be constructed in a manner known tothose skilled in the art and hence has been only partially shown forpurposes of simplicity. Briefly, the tool 48 b included an anvil housing54 b which terminates at one end in a swage anvil portion 56 b and abucking member 49.

The symmetrically shaped, tubular collar 14 b is adapted to be locatedover the shank 15 b and, with the workpieces 18 b, 20 b moved together,will be in radial alignment with some of the lock grooves 26 b. Withactuation of the tool 48 b, the swage anvil portion 56 b moves againstthe collar 14 b with the bucking member 49 resisting the axial forceapplied thereby; the resultant pushing force causes the workpieces 18 band 20 b to be pressed together. As this relative force increases theswage anvil portion 56 b will move over the collar 14 b resulting inswaging of the collar 14 b into the lock grooves 26 b of pin 12 b.Subsequently, upon further actuation of the tool 48 b, the anvil portion56 b will be removed from the swaged collar 14 b.

Note that in the stump version of FIG. 6, the anvil portion 56 b willprovide the same desired overpacking of the collar 14 b into the lockgrooves 26 b resulting in a desirable high, retained preload on thefastened joint of the yield point of the pin 12 b. While collar 14 b isshown as a tubular collar in FIG. 6 for securing workpieces 18 b and 20b of metal, a flanged type collar would be used to secure workpiecesmade of composite materials.

Having described the presently preferred embodiments of the invention,it is to be understood that the invention may be otherwise embodiedwithin various functional equivalents disclosed within the scope of theappended claims.

1. A swage type fastener which adequately secures a plurality ofworkpieces together in a fastened joint in a plurality of applicationshaving different load requirements, the fastener comprising: (a) a pinselected from a plurality of pin members of different diameters havingan elongated shank which is located in aligned openings in theworkpieces and terminating at one end in an enlarged head and at itsopposite end in a grooved portion comprising a plurality ofcircumferentially extending lock grooves and crests; (b) a tubularcollar selected from a plurality of collars of different materials, thecollar being swaged into the lock grooves whereby the workpieces areadequately secured together in the plurality of applications havingdifferent load requirements, the collar having collar grooves andshoulders interlocking the lock grooves and crests, the pin and thecollar being of different materials having shear strengths of differentmagnitudes with the ratio of such shear strengths of the pin to thecollar being such that crushing of the pin in swage is substantiallyavoided in the plurality of applications having different loadrequirements; (c) the pin having a uniform lock groove and crestgeometry, wherein the lock grooves are provided with the longest widthrequired for collars of lower strength for a shear application orgreater strength for a tension application and the crests are providedwith the longest width required for collars of greater strength for thetension application whereby the fastener provides satisfactory clamp andtensile loads and resistance to failure to secure the fastened jointtogether in the plurality of applications having different loadrequirements, wherein the applications are selected from the groupconsisting of shear, shear/tension, tension, shear composite,shear/tension composite and tension composite applications; (d) theuniform lock groove and crest geometry for the pin is used in theplurality of applications with one or more pins of the selected pindiameter to adequately secure the plurality of workpieces together inthe plurality of applications having different load requirements; and(e) the difference in width of the lock grooves in the tensionapplication is not greater than ten percent of the width of the lockgrooves in the shear application.
 2. The fastener of claim 1 wherein thecollar of lower strength has a shear strength of about 64% of the shearstrength of the collar of greater strength.
 3. The fastener of claim 1wherein the collar of lower strength is made of an aluminum alloy andthe collar of higher strength is made of a titanium alloy.
 4. Thefastener of claim 1 wherein the plurality of collars are made oftitanium alloys, aluminum alloys or steel alloys.
 5. The fastener ofclaim 1 wherein the lock grooves are overpacked in the range of 17% to25%.
 6. The fastener of claim 1 wherein the workpieces are made ofmetal, composites or combinations thereof.
 7. The fastener of claim 1wherein the plurality of applications are shear, shear/tension, shearcomposite or shear/tension composite applications and the plurality ofcollars of different materials used in such applications have about thesame outside diameter and are configured to be swaged into the lockgrooves of the pin with an installation tool having a swage anvil with auniform swage cavity.
 8. The fastener of claim 1 wherein the fastenerfastens workpieces that vary in thickness up to ⅛ of an inch.
 9. A swagetype fastener which adequately secures a plurality of workpiecestogether in a fastened joint in three or more applications havingdifferent load requirements, the fastener comprising: (a) a pin selectedfrom a plurality of pin members of different diameters having anelongated shank which is located in aligned openings in the workpiecesand terminating at one end in an enlarged head and at its opposite endin a grooved portion comprising a plurality of circumferentiallyextending lock grooves and crests; (b) a tubular collar selected from aplurality of collars of different materials, the collar being swagedinto the lock grooves whereby the workpieces are adequately securedtogether in the three or more applications having different loadrequirements, the collar having collar grooves and shouldersinterlocking the lock grooves and crests, the pin and the collar beingof different materials having shear strengths of different magnitudeswith the ratio of such shear strengths of the pin to the collar beingsuch that crushing of the pin in swage is substantially avoided in thethree or more applications having different load requirements; (c) thepin having a uniform lock groove and crest geometry, wherein the lockgrooves are provided with the longest width required for collars oflower strength for a shear application or greater strength for a tensionapplication and the crests are provided with the longest width requiredfor collars of greater strength for the tension application whereby thefastener provides satisfactory clamp and tensile loads and resistance tofailure to secure the fastened joint together in the three or moreapplications having different load requirements, wherein theapplications are selected from the group consisting of shear,shear/tension, tension, shear composite, shear/tension composite andtension composite applications; and (d) the uniform lock groove andcrest geometry for the pin is used in the three or more applicationswith one or more pins of the selected pin diameter to adequately securethe plurality of workpieces together in the three or more applicationshaving different load requirements.
 10. The fastener of claim 9 whereinthe collar of lower strength has a shear strength of about 64% of theshear strength of the collar of greater strength.
 11. The fastener ofclaim 9 wherein the collar of lower strength is made of an aluminumalloy and the collar of higher strength is made of a titanium alloy. 12.The fastener of claim 9 wherein the plurality of collars are made oftitanium alloys, aluminum alloys or steel alloys.
 13. The fastener ofclaim 9 wherein the lock grooves are overpacked in the range of 17% to25%.
 14. The fastener of claim 9 wherein the workpieces are made ofmetal, composites or combinations thereof.
 15. The fastener of claim 9wherein the three or more applications are shear, shear/tension, shearcomposite or shear/tension composite applications and the plurality ofcollars of different materials used in such applications have about thesame outside diameter and are configured to be swaged into the lockgrooves of the pin with an installation tool having a swage anvil with auniform swage cavity.
 16. The fastener of claim 9 wherein the fastenerfastens workpieces that vary in thickness up to ⅛ of an inch.
 17. Thefastener of claim 9 wherein the difference in width of the lock groovesin the tension application is not greater than ten percent of the widthof the lock grooves in the shear application.
 18. A swage type fastenerwhich adequately secures a plurality of workpieces together in afastened joint in a plurality of applications having different loadrequirements, the fastener comprising: (a) a pin selected from aplurality of pin members of different diameters having an elongatedshank which is located in aligned openings in the workpieces andterminating at one end in an enlarged head and at its opposite end in agrooved portion comprising a plurality of circumferentially extendinglock grooves and crests; (b) a tubular collar selected from a pluralityof collars of different materials, the collar being swaged into the lockgrooves whereby the workpieces are adequately secured together in theplurality of applications having different load requirements, the collarhaving collar grooves and shoulders interlocking the lock grooves andcrests, the pin and the collar being of different materials having shearstrengths of different magnitudes with the ratio of such shear strengthsof the pin to the collar being such that crushing of the pin in swage issubstantially avoided in the plurality of applications having differentload requirements; (c) the pin having a uniform lock groove and crestgeometry, wherein the lock grooves are provided with the longest widthrequired for collars of lower strength for a shear application and thecrests are provided with the longest width required for collars ofgreater strength for a tension application whereby the fastener providessatisfactory clamp and tensile loads and resistance to failure to securethe fastened joint together in the plurality of applications havingdifferent load requirements, wherein the applications are selected fromthe group consisting of shear, shear/tension, tension, shear composite,shear/tension composite and tension composite applications; and (d) theuniform lock groove and crest geometry for the pin is used in theplurality of applications with one or more pins of the selected pindiameter to adequately secure the plurality of workpieces together inthe plurality of applications having different load requirements. 19.The fastener of claim 18 wherein the collar of lower strength has ashear strength of about 64% of the shear strength of the collar ofgreater strength.
 20. The fastener of claim 18 wherein the collar oflower strength is made of an aluminum alloy and the collar of higherstrength is made of a titanium alloy.
 21. The fastener of claim 18wherein the plurality of collars are made of titanium alloys, aluminumalloys or steel alloys.
 22. The fastener of claim 18 wherein the lockgrooves are overpacked in the range of 17% to 25%.
 23. The fastener ofclaim 18 wherein the workpieces are made of metal, composites orcombinations thereof.
 24. The fastener of claim 18 wherein the pluralityof applications are shear, shear/tension, shear composite orshear/tension composite applications and the plurality of collars ofdifferent materials used in such applications have about the sameoutside diameter and are configured to be swaged into the lock groovesof the pin with an installation tool having a swage anvil with a uniformswage cavity.
 25. The fastener of claim 18 wherein the fastener fastensworkpieces that vary in thickness up to ⅛ of an inch.